Creature — Merfolk Wizard 1/1, 1W (2)
Common
Whenever a Merfolk you control becomes tapped, you may gain 1 life.
Though the currents of the Lanes shift every year, the merrow never lose track of where they are or where they are going.
Illus. Dan Scott

10/1/2007: This is a triggered ability, not an activated ability. It doesn't allow you to tap the creature whenever you want; rather, you need some other way of tapping it, such as by attacking with the creature.
10/1/2007: For the ability to trigger, the creature has to actually change from untapped to tapped. If an effect attempts to tap the creature, but it was already tapped at the time, this ability won't trigger.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander
Legal in Modern